31 115 
portion to the distance D. The table is divided into two groups of shots, fired in 
October and January respectively. The ratio shown in the last column is fairly 
constant in each group, considering the wide range which the results cover, but is 
higher for the Uctobey shots than for those fired in the winter month. The results 
of shot 66 are of special interest, and strongly support the suggested theory of the 
action of the gauges. 
TasLe VII. 
d, = depth of charge (feet). 
d, = depth of gauges (feet). 
D = distance from charge to gauges (feet). 
q = weight of extruded plasticine (grams). 
Charge. Shot. d,. | ds. D. I(p>0°3). Fig. q: iGo 
i | | 
October. | | 
267 hs. 80/20 Amatol — - 27 | 344 30 50 265 | 7 “$8 3°32 
” ” ” : STC OA 54; +50 265 10 “86 3°24 
akg an SUiaer 228 HUE Srl vino) | ara a Ty “85 4-9] 
1,000 Ibs. T.N.T.  - = - | 32 Sltheee On| 120) y =235059)) 20 73 en 
” ” oe) Ace Aes ator Sid On ZO ees235 20 72 3°06 
” ” at Pom ye lene 51k = 40 Tee We G8} 20 1-54 2-92 
40 Ibs. 40/60 Amatol - -| 34 18 12 264 160") 3 52 3°25 
ee st at Sy) hs 18 12 265 “160 13 50 3°12 
| | 
January. | | 
(OOO issstaNelo ee == = |) 20 514| 40 Tl. We 05% 20 1-19 3-25 
% 5 Seles Fay 59h re ola" 0 75 “53 20 1-10 2-08 
40 Ibs, 40/60 Amatol eeet|| 56 EI Oh BN “115 Ney. || oF 2-35 
ets eo as So Sys 18 | 21 25 “170 13 “34 2-00 
300 Ibs. 40/60 Amatol =e |) ctl 166 34 744] 40 “442 1 ois | Bose! 
Sagat ull = EH 266 34h' 945) 60 RBS | 1 SFB al © 2815) 
cs = S - - | 66 344; 1145) 80 -120 l 203 2-19 
Jie Te bm 35 - 66 345 1345 100 060 l SINS || Tee 
of a gy =} en 66 345 1545 120 “032 1 O72 | 2°25 
For the purpose of the symmetry test for which these gauges were principally 
designed it is not very important to know what they actually measure, but it is 
necessary to take account of the fact that the results do not vary in simple inverse 
proportion to the distance from the charge, as they would (approximately) with a 
gauge which measured either the maximum pressure or the whole time-integral of 
the pressure. The symmetry tests (Section 5) were carried out in nearly all cases 
with the plasticine gauges at a distance of 50 feet from a 30U-Ib. charge and at 
corresponding distances from charges of different size, and under these conditions 
a difference of 10 per cent. in the plasticine measurements represents a difference 
of only 7 per cent. in the whole time-integral of pressure. The results recorded in 
Table II. were therefore corrected in this ratio. For example, in the case of Shot 37 
the two groups of plasticine gauges at opposite sides of the charge gave results 
in the ratio 100:107; this was corrected to 100: 105, which represents the ratio 
of the distances at which the two groups of gauges would have given equal results. 
It is of interest to note that plasticine gauges hung a few feet below the surface 
of the water give evidence of the abrupt cessation of the pressure due to the reflected 
tension wave (Figs. 8, 9, and 10), the extruded plasticine being torn by its own 
momentum right out of the neck of the gauge, like a plant pulled up by the root. 
When the gauges are at a somewhat greater depth the stalk of plasticine is generally 
broken off a little outside of the neck, and at still greater depths the stalk remains 
entire. 
(21) Methods of laying out the Charge and Gauges 
in the Water. 
The method adopted in all but a few cases was to hang the charge and gauges 
from floats lashed to a grass hawser at measured intervals. The “ Malapert”’ being 
laid with the wind on her starboard quarter the gear was paid out on that side and 
dropped astern with the drift of the vessel. When the inboard end of the grass was 
Nn 4 
